Reject, modify and retest, or accept the hypothesis
True or False: Hypotheses can be proven.
False, hypotheses are never proven. Instead they are not disproven.
Quantitative descriptions use _______ to describe a feature while qualitative descriptions use _______ to describe a feature.
Quantitative uses measurements
Qualitative uses words
What are the two ways geologists measure orientation?
Strike (facing angle from true North)
Dip (angle from flat orientation)
What is the age range that geologists measure in geology?
Anywhere from 0 seconds to 4.5 billion years
What is the principle that states that the physical laws (e.g. gravity) work the same today as they did in the past?
The principle of uniformitarianism
What are the ways geologists depict the subsurface?
Block Diagram
Cross Section
Stratigraphic Section
Who developed the hypothesis of continental drift?
Alfred Wegner
When did he develop this hypothesis?
1915
What lines of evidence did he use to support his hypothesis?
Continents fit together like puzzle pieces
Fossil distribution
Mountain belts lining up
Permian glaciation
What was the name given to the supercontinent that formed when all the continents came together?
Pangea
How long ago did that supercontinent exist?
300 Ma – 175 Ma Ago
What could Wegner not explain about continental drift?
The mechanism of how the continents moved away from each other.
What piece of evidence came later that supported continental drift?
Magnetism in the oceanic crust showing sea floor spreading.
How do plates move relative to each other along a transform boundary?
they slide past eachother
How are transform plate boundaries related to convergent and divergent plate boundaries?
they connect any boundaries
What happens to surface features that are on both sides of a transform fault?
will become offset
What is the name of the transform fault that is the boundary between the Pacific plate and the North American plate in California?
san andreas
How thick is the lithosphere at an ocean ridge?
10km
How thick is the lithosphere at a continent?
125-200km
What is the name of the weakened layer that the lithosphere moves over?
ASthenosphere
What are the three explanations of why the plates move?
-ridge push (divergent)
-slab pull (weighs restdown)
-convection in the mantle
How quickly do plates move?
2-10cm per yr
Why is the island of Kauai no longer volcanically active?
position on the pacific plate is no longer a hotspot
What are the different ways that we explore the sea floor?
SONAR
Submersible
Drilling rig on boat
Satellites
A trench being offshore is typical of which type of continental margin?
An active continental margin
A broad continental shelf being offshore is typical of which type of continental margin?
A passive continental margin
Which feature has the greatest sloping angle: continental shelf, continental slope, or continental rise?
Continental Slope at 4-5
What type of crust underlies the continental shelf?
Continental Crust
What type of crust underlies the abyssal plains?
Oceanic Crust
What seafloor features can form due to hot spot volcanism?
Seamounts
Oceanic Plateaus
The temperature at which the Earth’s magnetic field is locked into a rock is called what?
The Curie Point
Magnetism on the sea floor was matched with what that we had already dated?
Volcanic rocks on land
How did we confirm the magnetism dating of the seafloor?
By matching the dating of fossils in sediment cores at predicted areas.
What is considered tectonic activity?
Earthquakes
Volcanoes
Mountain Building
Why do earthquakes happen at plate boundaries?
The tectonic plates are moving in different directions
What are the types of plate boundaries?
Divergent
Convergent
Transform
What type of plate boundary does this symbol represent?_^_^_^
Convergent
What are the three types of convergent plate boundaries?
Oceanic-Oceanic
Oceanic-Continental
Continental-Continental
What type of plate boundary is where new crust is formed?
Divergent
What type of plate boundary is where crust is destroyed?
Convergent Oceanic-Oceanic
Convergent Oceanic-Continental
What causes back-arc spreading?
Trench Rollback
What type of boundary has the largest magnitude earthquakes?
Convergent
What type of convergent plate boundary does not have a subduction zone?
Continental-Continental
what r the 3 different faults
-normal
-reverse
-strike
whats the epicenter of an earthquake
location of surface, above hypocenter
what mag of earthquakes would you expect at a divergent plate boundary
small-mod
which type of plate bounary would u expect to find the deepest earthquake
convergent/subduction
what type do u expect to see convental collision
reverse faults
what r some ways that earthquakes can occur in the middle of a tectonic plate
-reactivation volc
-hot spot volc
-mid continent rifting volc
whats the difference between bodywaves & surface waves?
body waves travel through surface
what kind of seismic wave can only travel solids
s-waves
how many seismic stations do you need data from to locate an earthquake
@least 3
an m7 quake is how many x's more powerful than an m3 quake
each M=32. 1milli times more powerful
liquefaction is caused by?
shaking cuases could lead graines to lose grain
whats events could lead to a tsunami
-quakes
-volc eruptions
-landslides
ocean trench
an oceanic plate forms
an oceanic plate bending in order to go down the subduction zone at a convergent plate boundary.
volcanism at a hot spot.
island arc
volcanism at an island arc.
plates pulling away from each other at a divergent plate boundary.
an oceanic plate bending in order to go down the subduction zone at a convergent plate boundary
ocean plateu
volcanism at a hot spot
plates pulling away from each other at a divergent plate boundary.
an oceanic plate bending in order to go down the subduction zone at a convergent plate boundary.
hot spot
plates pulling away from each other at a divergent plate boundary.
an oceanic plate bending in order to go down the subduction zone at a convergent plate boundary.
sub canyon & fan
turbidity currents flowing down the continental slope.
an oceanic plate bending in order to go down the subduction zone at a convergent plate boundary.
passive continental margin
plates pulling away from each other at a divergent plate boundary.
an oceanic plate bending in order to go down the subduction zone at a convergent plate boundary.
back arc
an island arc that rose up and partially separated a small ocean basin from the main ocean. In this case there is also sea-floor spreading occuring in the small ocean basin.
an oceanic plate bending in order to go down the subduction zone at a convergent plate boundary.
abyssal plain
Originally feature 8 formed by sea-floor spreading, but the very smooth surface of this feature results from a burial by a thin layer of sediment.
an oceanic plate bending in order to go down the subduction zone at a convergent plate boundary.
mid ocean ridge
plates pulling away from each other at a divergent plate boundary.
an oceanic plate bending in order to go down the subduction zone at a convergent plate boundary.
fracture zone
is an old, inactive portion of a transform plate boundary. It appears as a discontinuity in the sea floor because it separates sea floor of two different ages. But the sections of sea floor on both sides of this feature are both moving in the same direction now.
trench & island arc related
feature 1 is created by bending of an oceanic plate going down a subduction zone, and that same plate begins to melt, once it gets deep enough, and the resulting magma rises to form feature 2.
ocean plateu & hot spot
feature 4 is created by bending of an oceanic plate going down a subduction zone, and that same plate begins to melt, once it gets deep enough, and the resulting magma rises to form feature 3.
middle ridge & fracture
feature 9 was created by two plates pulling away from each other and feature 10 is an inactive remant of a transform plate boundary that formed at a jog within feature 9
Where was the oceanic plateau relative to the hot spot 20 million years ago?
half the distance as today.
What was the length of the linear chain of islands (between features 3 and 4) 20 million years ago?
half as long as today.
Which way is the plate on which the oceanic plateau rests moving relative to the hot spot at depth? Assume that on the main figure you are looking north.
northwest
How wide was the narrow sea between the volcanic islands and the western continent 20 million years ago?
didnt exist
How wide was the narrow ocean between the central and eastern continents 20 million years ago?
narrower
How wide do you think the narrow ocean between the central and eastern continents will be 20 million years into the future?
nearly twice as wide as it is today
What do you think might happen to the oceanic plateau (feature 3) 20 million years into the future?
may collide with trench
What technique is used to determine the depth to a boundary in the Earth?
Seismic Reflection
Seismic waves bend in which direction when entering a faster material?
Towards the boundary
Where is the crust the thickest?
Underneath Mountains
Where is the crust the thinnest?
Underneath mid-ocean ridges
What is the name of the boundary between the crust and the mantle?
The Mohorovicic Discontinuity (The Moho)
What happens to P-wave velocity in the asthenosphere? Why?
It decreases due to the asthenosphere being partially melted and hence less rigid
What type of seismic waves can not travel through the outer core? Why?
S-waves, due to the fact that the outer core is liquid
Recap
Can p-waves from an earthquake be detected all over the surface of the Earth?
No, there is a shadow zone on the Earth where P-waves can not be detected
What is the difference between the outer core and the inner core?
The outer core is liquid while the inner core is solid
What is the composition of each layer of Earth?
Crust: Oceanic (Basalt) and Continental (Granite)
Mantle: Peridotite
Core: Iron
Where does the heat from the Earth originally come from?
Radioactive Decay
Leftover energy from the formation of the Earth
What is the coolest layer of the Earth?
The Crust
_______________________
How does back-arc spreading occur?
A subducting slab steepens its angle of subduction causing trench rollback. This pulls the volcanic island arc towards the trench, thinning the oceanic crust behind the islands eventually forming a spreading center there.
Seismic waves travel faster through what types of material?
Denser or more rigid material
In which areas would you expect to find the largest magnitude earthquakes?
Subduction Zones
A tsunami is caused by what?
A displacement of water either by earthquake, volcanic eruption or landslide into water.
What is the name of the most recent supercontinent that formed when all the continents came together?
Pangea
What type of fault is typically seen in convergent boundary?
Reverse Faults
Where is oceanic crust destroyed?
Subduction Zones
What type of continental margin has a trench offshore?
Active
The temperature at which the Earth's magnetic field is locked into a rock is called what?
